I was thinking about this for a bit. Like many on here, I massively rate the lad and think his long term future should be as a CM.
However, it looks like Catts and Gardner will be the first-choice partnership, with Vaughan offering cover, and Meyler when he's back fit. On the left (presuming SB is telling the truth and we're done buying) we've only really got Malbranque and Richardson. I'd rather see Colback get the games to develop as a player, and therefore, if he's willing and looks ok in training, I'd give him that LM spot. Richardson at LB (Bardo at RB) and we'd have his pace as support, and Colback's defensive capability when we're under the cosh.
If Catts and Gardner start in the middle, then the choice for Colback is LM or bench. Give him LM, give him minutes on the pitch, let him develop as a player and let's see where it goes..?
Bardsley - O'Shea - Bramble - Richardson
Larsson - Catts - Gardner - Colback
Sess - Gyan
....I wouldn't be unhappy with that at all. Defensive discipline with help from midfield if needed. Left footers on the left, right footers on the right, goals throughout the team from every position bar GK..